Question 1

Which of the following best describes the sequence of events in a plant signal transduction pathway in response to light?

Accepted Answer

Reception by a receptor, production of second messengers, activation of transcription factors, cellular response

Question 2

A plant is exposed to a unilateral light source. According to the acid growth hypothesis, what is the role of auxin in the elongation of cells on the shaded side?

Accepted Answer

Auxin increases proton pump activity, lowering cell wall pH and activating expansins that loosen the wall

Question 3

Which experiment led to the discovery of the first plant hormone, and what was the hormone?

Accepted Answer

Fritz Went’s agar cube experiment; the hormone was auxin

Question 4

A gardener applies a synthetic auxin herbicide to a lawn. What is the most likely outcome for dicot weeds?

Accepted Answer

The dicot weeds will die due to auxin overdose disrupting normal growth

Question 5

Which hormone is primarily responsible for promoting seed dormancy and enhancing drought tolerance in plants?

Accepted Answer

Abscisic acid (ABA)

Question 6

A mutant maize plant germinates early, even under dry conditions. Which hormone pathway is most likely disrupted?

Accepted Answer

Abscisic acid (ABA) signaling

Question 7

Which combination of hormones is required for fruit set in many plants, such as grapes?

Accepted Answer

Auxin and gibberellin

Question 8

A plant’s apical bud is removed. What hormonal change occurs, and what is the result?

Accepted Answer

Auxin levels decrease, allowing cytokinins to promote axillary bud growth

Question 9

Which hormone is most closely associated with the triple response in seedlings, and what is one effect of this response?

Accepted Answer

Ethylene; inhibition of stem elongation

Question 10

A plant is exposed to drought conditions. Which hormone is most likely to accumulate, and what is a physiological effect?

Accepted Answer

Abscisic acid (ABA); closure of stomata to reduce water loss

Question 11

Which of the following best explains why a leaf falls from a tree in autumn?

Accepted Answer

A change in the balance of auxin and ethylene triggers the formation of an abscission layer

Question 12

Which of the following is a real-world application of gibberellins in agriculture?

Accepted Answer

Spraying seedless grapes to increase fruit size

Question 13

A plant mutant is insensitive to ethylene. What phenotype would you expect when the seedling is exposed to mechanical stress?

Accepted Answer

The seedling fails to undergo the triple response and continues normal elongation

Question 14

Which hormone is most directly involved in stimulating cell division in plant shoots and roots?

Accepted Answer

Cytokinin

Question 15

A scientist wants to promote lateral root formation in a plant cutting. Which hormone should be applied, and why?

Accepted Answer

Auxin, because it stimulates root formation and branching

Question 16

Which of the following best describes the role of second messengers in plant signal transduction?

Accepted Answer

They transfer and amplify signals from receptors to proteins that cause responses

Question 17

A plant is genetically modified to overproduce cytokinins. What is a likely phenotype?

Accepted Answer

Increased shoot growth and delayed leaf senescence

Question 18

Which hormone is most closely associated with fruit ripening and senescence?

Accepted Answer

Ethylene

Question 19

A plant is exposed to continuous light and fails to develop chlorophyll, remaining pale and elongated. Which process is most likely disrupted?

Accepted Answer

De-etiolation (greening) response

Plant Signaling and Hormones: Mechanisms and Functions

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